Thermal expansion bleed-off system

ABSTRACT

In combination with a water piping arrangement having a backflow preventer and a water heater with a standard temperature-pressure relief valve, an auxiliary pressure-relief device is installed in the cold-water supply line to the water heater and this auxiliary relief device is adapted to activate at a pressure slightly below that which activates the temperature-pressure relief device, thereby releasing water and excessive pressure buildup in the piping arrangement due to thermal expansion of water in the water heater. The water released in order to prevent the excessive pressure buildup is routed to a floor drain via flexible plastic tubing.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is closely related to and claims priority from U.S.Provisional Application Ser. No. 60/734,421 filed Nov. 8, 2005.

FIELD OF THE INVENTION

The present invention relates generally to apparatus for protectingplumbing systems from over-pressurization due to thermal expansion. Moreparticularly, this invention offers an improved system for protectingagainst over-pressurization of water lines and home hot water heatersconnected to a water supply equipped with a back-flow prevention device.

BACKGROUND OF THE INVENTION

Prior to the conception and development of the present invention, homeand building hot water heaters have for many years been equipped with asafety device called a Temperature-Pressure Relief Valve (TPR valve).This prevents an explosion of the tank in the event of overheating orover-pressurization for any reason. One common problem with the TPRvalves is leakage when they are older, or when particles get trapped inthem due to occasional opening. This latter problem has become morecommon over the past 20 years due indirectly to changes in buildingcodes and/or plumbing practices.

It is commonplace now to have a back-flow preventer or pressure-reducingvalve on the total water supply to a house. This prevents anypotentially contaminated water from inside the house migrating back intothe water main should there be a temporary drop in water main pressure,as might result from a broken water main. Consequently, after asubstantial use of hot water in a house followed by no water use for aperiod thereafter, the cold water that refilled the tank gets heated tothe normal hot water tank temperature and that water must expand involume accordingly. With all avenues of flow closed off now, pressurebuilds up in the entire water supply system of the house until the setpressure of the TPR valve is reached and it opens to leave water out.These TPR valves are not meant to handle frequent opening and closing.In addition, such openings cause hot water to be spewed out with thepotential for scalding someone's feet or ankles. Even after returning tothe essentially closed position, the TPR valve sometimes continuesdripping water constantly. As related in U.S. Pat. No. 6,698,714, someresidents have responded to this by plugging the TPR outlet pipe therebycreating the very hazardous potential for rupturing the hot water tank.

In response to these hazards, building codes and/or plumbing practiceshave resorted to installing an expansion tank on the cold water inletline to the water tank. These come in various sizes and typically have abuilt-in rubber bladder that expands in volume when the water pressureexceeds the normal. Then, when water is used somewhere in the house, thebladder pushes water out to create volume for the next episode ofthermal expansion. These expansion tanks are readily available atplumbing supply stores and major home improvement retailers like Lowe'sand Home Depot. Besides their expense, they occupy space near the hotwater heater, they place stress on the water lines, and they are subjectto failure either by corrosion or decay of the internal rubber bladder.In spite of these drawbacks, there does not appear to be any significantalternatives being offered to homeowners. Hence, there is clearly a needfor a better solution to the thermal expansion problem than theexpansion tank.

Related prior art extends back at least as far as U.S. Pat. No.1,694,492, which describes a temperature-pressure relief valve for hotwater heaters. Such devices were relatively trouble-free untilwhole-house back-flow preventers became commonplace. In response to theleakage problems that frequently began occurring, expansion tanksemerged as the solution to this relatively new problem. Besides theexpense and space occupied by these tanks, they have experiencedproblems of their own due to corrosion and bladder failures. Hence,there is a need for a less-expensive, longer-lasting replacement forfailed expansion tanks.

Alternatives to the expansion tank do appear in the prior art. U.S. Pat.No. 4,745,945 teaches a toilet fill valve with an integral pressurerelief device. However, fill valves occasionally need replaced, and aplumber or homeowner is likely to overlook this feature as they seek theleast-expensive option, and this functionality would often be lostsubsequent to initial use. The “Installation Instructions for the WattsRegulator Company's Model 53 and 30L Pressure Relief Valves” teaches theuse of their model 53 as an auxiliary bleeder for thermal expansionrelief. Neither of these two references mentions replacement ofexpansion tanks. In addition, it should be noted that devices like theWatts Model 53 do not come with a tubing connection at the outlet end.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, in a water pipingarrangement having a backflow preventer and a water heater with astandard temperature-pressure relief valve, an auxiliary pressure-reliefdevice is installed in the cold-water supply line to the water heaterand this auxiliary relief device is adapted to activate at a pressureslightly below that which activates the temperature-pressure reliefdevice, thereby releasing water and excessive pressure buildup in thepiping arrangement due to thermal expansion of water in the waterheater. The cold water released is routed via tubing to the floor drainthat is in the vicinity of the water heater

In a second aspect of the invention, all the necessary pieces forreplacing an expansion tank are arranged and offered as a kit.

OBJECTS OF THE INVENTION

The need for a device or apparatus such an expansion tank in the waterfeed line to a hot water heater has been well established asforward-only flow home water supply systems have become more common. Itis, therefore, one of the primary objects of the present invention toprovide an improved and less expensive replacement for a worn-outexpansion tank.

It is also an object of the invention to provide an improved method ofprotecting water piping arrangements in new construction.

It is also an object of the invention to make the improved methodavailable to homeowners and plumbers in the form of a kit for simple andeasy installation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview of a hot water heater and piping arrangementshowing the auxiliary pressure relief apparatus.

FIG. 2 is a close-up side view of an installed thermal expansion bleedvalve and the tubing attachment.

FIG. 3 is a frontal view of the three-piece kit for replacement ofthermal expansion tanks.

DESCRIPTION OF THE PRESENTLY PREFERRED AND ALTERNATE EMBODIMENTS OF THEINVENTION

Prior to proceeding with the more detailed description of the presentinvention it should be noted that, for the sake of clarity, identicalcomponents which have identical functions have been designated byidentical reference numerals throughout the several views illustrated inthe drawings.

In FIG. 1, an overview the piping and hot water heater arrangement 10 isdepicted with the auxiliary pressure bleed-off valve 22 installed in thecold water supply line 18 at the branch tee 20. A pressure regulator orbackflow prevention valve 16 creates the blocked-in situation that leadsto the pressure buildup during water heating. Also shown is thetemperature-pressure relief device 11 with its outlet drain pipe 14installed on water heater 36. The bleed valve drain hose 24 is alsoshown ending at floor drain 28. The tubing 24 is prevented from floppingaround by clamp 26 attached at one end to rigid drain pipe 14.

FIG. 2 provides a close-up side view of the thermal expansion bleedvalve 22 connected to the female threaded connection 20 off of the coldwater line 18 with the connection for the plastic tubing 24.

In another aspect of the invention depicted in FIG. 3, the invention isassembled into a kit targeted at replacement of expansion tanks. Thethree main pieces are attached to a printed cardboard backing 30 withplastic straps 32. The relief valve 22 could be a custom-made unit withthe desired cracking pressure and a ¾-inch male NPT inlet connection,and either a ¼-inch or ⅜-inch tubing connection on the other end, andconstructed of brass or stainless steel. Alternatively, relief valve 22could be a slightly adapted version of a commercially available devicesuch as Swagelock Company's poppet check valve part No. B-4CP2-100. Thesecond part of the kit would typically be about an 8-foot length ofeither ¼ or ⅜-inch diameter flexible plastic tubing, most likelypolyethylene or flexible PVC. The tubing would come with theappropriately sized ferrule 33 and nut 34 already attached to one end.The final piece of the kit would be a clamp to restrain the tubing fromexcessive movement by supporting it off of the rigid drain line. Thereare numerous existing designs that would suffice for this purpose, suchas simplified versions of standard laboratory thermometer clamps (FisherScientific).

While a presently preferred and various alternative embodiments of thepresent invention have been described in sufficient detail above toenable a person skilled in the relevant art to make and use the same, itshould be obvious that various other adaptations and modifications canbe envisioned by those persons skilled in such art without departingfrom either the spirit of the invention or the scope of the appendedclaims.

1. In combination with a water supply piping arrangement having abackflow preventer and a water heater with a standardtemperature-pressure relief valve, the improvement comprising a) abranch tee fitting with a threaded opening disposed 90 degrees to a coldwater supply line to said heater; b) an auxiliary pressure-relievingdevice connected in a branch of said tee and having an activationpressure below that of said temperature-pressure relief valve; and c)tubing connected to an outlet side of said pressure-relieving device andending at a gravity drain.
 2. The improvement, according to claim 1,wherein said pressure relieving device is a spring-loaded,fixed-pressure relief valve.
 3. The improvement, according to claim 1,wherein said pressure relieving device has a threaded male NPT inletconnection and a tube compression connection as the outlet connection.4. The improvement, according to claim 1, wherein said tubing isflexible.
 5. The improvement, according to claim 1, in which saidpressure relieving device is set to crack open at a water pressurebetween 50 and 200 psig.
 6. The improvement, according to claim 1wherein said pressure relieving device is set to crack open in a rangeof between about 10 to 40 psi below an opening pressure of saidtemperature/pressure relief valve on said water heater.
 7. Theimprovement, according to claim 3, wherein said male NPT connection is anominal ¾-inch diameter pipe size.
 8. The improvement, according toclaim 1, wherein said branch tee comprises a female ¾-inch NPT threadedopening at 90 degrees to a straight-through run for typical water flow,and wherein a main inlet and an outlet end of the tee fitting are one ofsoldered and welded to said cold-water supply lines.
 9. A kit forreplacing thermal expansion tanks associated with hot water tanksequipped with a standard temperature-pressure relief valve, said kitcomprising a) a fixed-pressure relief valve with about ¾-inch NPTthreads on a first end connection and a predetermined size of tubecompression fitting on a second end; b) a predetermined length ofplastic tubing having a predetermined OD with a matching size ferruleand nut attached to one end; and c) a clamp for supporting said tubingfrom a discharge pipe of said temperature-pressure relief valve.
 10. Thekit, according to claim 9, wherein said predetermined length of tubingis about 8 to 10 feet in length.
 11. The kit, according to claim 9,wherein said predetermined OD of said tubing is about ¼-inch to ⅜-inch.12. The kit, according to claim 9, wherein said predetermined size ofsaid compression fitting is between about ¼-inch and ⅜-inch.